A traditional travelling mold for forming plastic ribbed pipe and the like includes opposing mold block halves or sections which close with one another to form the pipe between the sections. The mold block sections open to release the pipe after its shape has been set.
In one known travelling mold configuration, the mold block sections are mounted in two separate endless tracks and the mold block sections move horizontally around the tracks. The mold block sections come together at what is known as the mold tunnel to form the pipe.
It is also possible to have all of the mold block sections move in a single horizontal track where facing mold block sections close along one side of the track to form the mold tunnel and where they open from one another along the other side of the track.
In horizontally travelling molds the mold block sections have a geared surface which engages a drive gear for driving the mold block sections around the track. Accordingly, each mold block section forms a link in the drive chain and this necessitates the use of side-by-side mold block sections completely around the track; otherwise the drive chain would be broken.
The mold block sections themselves are intricate in construction because of the many functions that they must perform in making the plastic pipe. Therefore, travelling molds formed with continuous lengths of mold block sections are high in cost. Furthermore, if an individual mold block section must be removed for maintenance purposes or the like, the entire mold must be shut down until that particular mold block section is replaced which results in lower production and associated down time costs.